From the publisher's website (2006 paperback):

It was the best thing that ever happened to him.

It was his god’s blessing.

It was hell.

Vell was content to be a mere warrior in the Thunderbeast tribe, staying behind on the hunt to guard the camp.

But then something alien awakened deep within him, the spirit of a behemoth that he could not control. With it came attacks from the sky, visitors from far lands, and a mysterious command from their ancestral totem: Find the living. And this time, no one was going to let him just stay behind.